The Bipolarity Index: a clinician-rated measure of diagnostic confidence.

Background: The Bipolarity Index is a clinician-rated scale that rates cardinal features of the disorder across five domains: signs and symptoms, age of onset, course of illness, response to treatment, and family history. We tested the Index in routine clinical practice to identify the optimal cut-off for distinguishing bipolar from non-bipolar disorders.

Method: Sequential patients in a private practice were rated with the Bipolarity Index (n=1903) at intake. Diagnoses were made with the MINI-6.0.0 International Neuropsychiatric Interview according to DSM-IV-TR criteria, except that cases of antidepressant-induced mania and hypomania were included in the bipolar group. A subset completed the self-rated Mood Disorder Questionnaire (MDQ) (n=1620) or Bipolar Spectrum Diagnostic Scale (BSDS) (n=1179). The primary analysis compared Bipolarity Index scores for bipolar vs. non-bipolar patients using receiver operator curves (ROC) to determine the optimal cut-off score. Secondary outcomes repeated this analysis with the MDQ, MDQ-7 (using only the symptomatic items of the MDQ) and BSDS.

Results: At a cut-off of ≥50, the Bipolarity Index had a high sensitivity (0.91) and specificity (0.90). Optimal cut-offs for self-rated scales were: MDQ: ≥7 (sensitivity 0.74, specificity 0.71); MDQ-7: ≥6 (sensitivity 0.77, specificity 0.77); BSDS: ≥12 (sensitivity 0.71, specificity 0.77).

Limitations: The study utilized one rater at a single practice site; the rater was not blinded to the results of the MINI.

Conclusion: The Bipolarity Index can enhance the clinical assessment of mood disorders and, at a score ≥50 has good sensitivity and specificity for identifying bipolar disorders.